Trinity College Colac announced on Sunday it had received approval from the Department of Health and Human Services to close the campus until Thursday to allow further tracing and testing to be conducted.

Trinity College Colac principal Paul Clohesy said on Saturday morning one of their Year 12 students tested positive to COVID-19.

It comes after the student's parent, a worker at Australian Lamb Colac, returned a positive COVID-19 test on Friday.

A statement from the school said a "deep clean" was currently well underway.

"Families should check their emails for further detail. Please take care of yourselves and check in on your loved ones. Stay safe and stay at home as much as possible," a statement on Facebook said.

The College said wearing a mask was a matter of personal choice and urged students and staff to refer to the DHHS website for guidance.

A third coronavirus case has since been linked to the Australian Lamb Colac cluster.

Contact tracing from Colac's two other active cases led to the detection of the case.

The third case is not a student of the school but is a close contact of the initial case.

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